(a) Technical Field
The present invention relates to a coolant reservoir tank for a fuel cell vehicle. More particularly, the present invention relates to a coolant reservoir tank for a fuel cell vehicle, which is positioned at a bottom of the vehicle such that coolant in a coolant line is collected to the reservoir tank by gravity when a fuel cell system is inactivated and the coolant in the reservoir tank is supplied to the coolant line by a vacuum pump during startup of the fuel cell system.
(b) Background Art
A fuel cell system generates electricity by converting chemical energy of fuel directly into electric energy. The fuel cell system generally comprises a fuel cell stack for generating electricity, a fuel supply system for supplying fuel (hydrogen) to the fuel cell stack, an air supply system for supplying oxygen in air, which is an oxidizing agent required for an electrochemical reaction, to the fuel cell stack, and a thermal and water management system for dissipating reaction heat of the fuel cell stack to the outside of the fuel cell system and controlling the operation temperature of the fuel cell stack.
The fuel cell system having the above configuration generates electricity by the electrochemical reaction of hydrogen as fuel and oxygen and exhausts heat and water as reaction by-products. Since in the fuel cell system, heat is concurrently generated with electricity during reaction, it is necessary to equip a means for cooling the fuel cell to prevent excessive increase of temperature in the fuel cell.
FIG. 1 is a conceptual diagram showing a conventional cooling system for a fuel cell vehicle. An intermediate heat exchanger 2 is used to cool a fuel cell stack 1, in which, when a first coolant absorbs heat of the stack 1 and transfers the heat to a second coolant in the intermediate heat exchanger 2, the second coolant is cooled in a radiator 3 to radiate heat.
In such a first cooling loop adapted for primarily cooling the stack 1, when the fuel cell system is inactivated, all coolant in the loop flows down to a coolant reservoir tank (water tank) provided beneath the fuel cell system, i.e., at the lowest portion of the vehicle due to gravity. On the other hand, during startup of the fuel cell system, when a vacuum state is created in the fuel cell system by a vacuum pump 4, the coolant in the reservoir tank returns to the inside of the fuel cell system by a pressure difference.
Such a coolant reservoir tank having the above function is necessary to both satisfy the sealing requirements of connection portions and ensure a high coolant supply capability in a vacuum state.
As shown in FIG. 2, in a conventional reservoir tank 100 for a fuel cell vehicle, a reservoir housing 11 and a cover 10 are joined together by means of bolts 102, the cover and a port 101 are also connected by the bolts 102, and a silicon pad 103 is mounted on the connection portions to maintain the air tightness.
However, the above-described structure has some drawbacks in that the assembling efficiency is deteriorated due to the large number of bolts 102 (approximately 80). Moreover, since the silicon pads 103 and 104 (shown in FIGS. 3 and 4) mounted between the reservoir housing 11 and the cover 10 and on the connection portion of the port 101 may be deformed by the fastening pressure caused when the bolts 102 are fastened, the air tightness is not maintained, causing a coolant leakage.
Moreover, during the startup of the fuel cell system, the vacuum state is not maintained in the system by the leakage of the connection portions, and thus the coolant may not be smoothly supplied to the system.
Furthermore, as shown in FIG. 4, a pipe 105 having a “⊂” shape provided in the reservoir housing 11, although it can suck the coolant at the bottom of the reservoir tank to enable coolant supply even if the vehicle is inclined on a slope, may cause a pressure drop, which prevents a smooth coolant supply even if the inside of the fuel cell system is under a vacuum condition.
The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person in the art.